AND GENERA OF PLANTS. 369' 



Hab. With the above, which it closely resembles, but is a more slender plant, with smaller 

 flowers; terminal leaflet largest, the lateral often small. Achenia a little bristly, sometimes with 

 only one awn, or even without any, in the same capitulum with most of the others possessing awns. 



Bidens * angustifolia; very smooth and herbaceous; leaves pseudopinnate, 

 in two or three pairs; segments narrow-lanceolate, acuminate, serrate, the low- 

 est leaflet sometimes divided ; panicle trichotomous, contracted ; sepals nearly 

 equal ; rays about five, longer than the disk ; achenium ciliate with erect bris- 

 tles, two-awned, the awns retrorse at the summit. 



Hab. With the above, from which it differs in the narrow and pinnated leaves ; the fruit has, 

 also, longer awns, and the pedicels are short. The stem twelve to eighteen inches high. Awns 

 of the achenium sometimes unequal, or of different lengths in the same capitulum. 



t BiDENS proper. 



Bidens *hirsuta; herbaceous, and more or less hirsutely pubescent; stem 

 quadrangular, grooved, trichotomous; leaves pseudopinnate, in two or three 

 pairs, the uppermost sometimes ternate, segments lanceolate, acuminate, in- 

 cisely serrate, lateral divisions with the base obliquely attenuated; rays none; 

 involucellum eight-parted, shorter than the involucrum; achenium subquad- 

 rangular, with a wide, circular, basal areole, the angles hirsute or scabrous 

 above; awns three, unequal, strongly retrorse barbellate. 



Hab. In Atooi. Two to three feet high, with a thick, hirsute, quadrangular stem, oppositely 

 branched. Leaves much like those of Agrimonia Eupatoria; hence, I suspect it is closely allied 

 to B. Wallichii. It is, however, destitute of rays. Outer involucrum with the segments connected 

 together at the base; the inner, also, about eight-leaved. Achenium linear, straight, smooth, except 

 the upper edges of the angles, which are ciliate with tubercular, short bristles; awns about three, a 

 third the length of the fruit, with strong, barbellate bristles their whole length. Hairs of the stem 

 broad, flat, membranaceous and acuminate. Branches of the stigma with long, acuminated, slender 

 points. 



*MICRODONTA. 



Capitulum many-flowered, heterogamous ; rays feminine in a single series, 

 (about five,) many-nerved. Discal florets hermaphrodite, tubular-campanu- 

 late, five-toothed, the tube short and slender. Receptacle flat, paleaceous; 

 palea oblong, similar with the inner involucrum. Involucrum double, the 

 outer six-leaved, foliaceous, the inner about five-leaved, discoloured, some- 

 what scarious. Achenia flatly compressed, those of the ray elliptic, mi- 

 VII. — 4 s 



